The poet's parting feelings in seeing off the giant Lulun are as follows: the poet is reluctant to part with his friends (or "thinking of friends"); The sadness when the poet and his friend are about to part; The poet's concern for his friend's difficulties and obstacles in this journey; Poets look forward to meeting their friends again (or "disappointment that they don't know when and where they will meet again")
I hope it helps you.